Production of the biocontrol agent Pantoea agglomerans PBC-1 in a stirred tank reactor by batch and fed-batch cultures
2010
Manso, Teresa | Nunes, Carla | Raposo, Sara | Lima-Costa, Maria Emília
Concerns about food safety as well as the development of resistance to many fungicides by major postharvest pathogens have increased recently. Biological control, using microorganisms antagonistic to the fungal plant pathogens, appears to be promising as an alternative to fungicides. The microbial biocontrol agent has to be produced on an industrial scale, maintaining its biocontrol efficacy. The purpose of the current study was to optimize the conditions for microbial biomass production of the biocontrol agent Pantoea agglomerans PBC-1 in a 2-l mechanically stirred reactor (STR), defining mixing and mass transfer technological parameters and the growth kinetics for different saccharides. In the batch mode, different impellers and spargers were tested. Despite the oxygen mass transfer improvement achieved with marine propeller combined with porous sparger, the biomass did not increase, if compared with the use of a Rushton turbine and L-sparger, pointing out the relevance of a radial flux for better broth homogenization. Different carbon sources were used: sucrose, glucose and fructose; each of which led to viable populations 3.9 × 109, 1.4 × 109, 3.9 × 109 c.f.u/ml, respectively, after 20 h of incubation. Fed-batch technology allows the maintenance of high cell viability for longer periods of time in the stationary growth phase, which can be crucial for the scale-up of biocontrol agent production process that is achieved together with a reduction of 85% on the incidence caused by the pathogens, brought about by fresh microbial biomass preparation on artificially wounded apples or oranges, stored for 7 days at 25°C against Penicillium expansum and Penicillium digitatum.
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